|KORNELSEN, K.C. - McMaster University|
|COULIBALY, P. - McMaster University|
Submitted to: Journal of Geophysical Research Atmospheres
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2015
Publication Date: 7/30/2015
Citation: Kornelsen, K., Cosh, M.H., Coulibaly, P. 2015. Potential of bias correction for downscaling passive microwave and soil moisture data. Journal of Geophysical Research Atmospheres. 120(13), 6460-6479. doi: 10.1002/2015JD023550.
Interpretive Summary: Satellite remote sensing soil moisture products are not available at scales which can be used for managing agriculture. Using a land surface model it is possible to downscale these products to more functional resolutions. This technique uses temporally stable patterns determined from in situ resources and community based land surface models at two U.S. watersheds to demonstrate the method and establish error criteria. The results of this study can be applied to new satellite products which will be useful to watershed managers and agribusiness professionals.
Technical Abstract: Passive microwave satellites such as SMOS (Soil Moisture and Ocean Salinity) or SMAP (Soil Moisture Active Passive) observe brightness temperature (TB) and retrieve soil moisture at a spatial resolution greater than most hydrological processes. Bias correction is proposed as a simple method to disaggregate soil moisture to a scale more appropriate for hydrological applications. Temporal stability of soil moisture and TB was demonstrated at the Little Washita and Little River Experimental Watersheds using in situ observations and the Community Microwave Emissions Model. Decomposition of the mean squared difference (MSD) between the watershed average soil moisture and TB showed bias was a major contributor to differences between watershed average and local scale soil moisture and TB, particularly at sites with high MSD. The mean RMSD between watershed average and local soil moisture was 0.04 m3m-3 and 0.06 m3m-3 at Little River and Little Washita respectively. Following a simple bias correction the RMSD was reduced to 0.03 m3m-3 at both sites. Considering multiple incidence angles at both horizontal and vertical polarization, bias correction of watershed average TBV reduced the RMSD by approximately 75% and 45% and TBH RMSD by 68% and 36% for Little River and Little Washita respectively at all incidence angles. Therefore, at sub-satellite grid scale, bias correction can be considered a viable technique for downscaling passive microwave observations and soil moisture retrievals.